The present invention relates to cinematographic apparatus in general, and more particularly to improvements in adjustable shutters which can be utilized in motion picture cameras for the making of exposures with short exposure times whose duration is determined in advance by appropriate setting of the apparatus, and exposures with longer exposure times as selected by the user from exposure to exposure subsequent to start of the respective exposure. Still more particularly, the invention relates to improvements in motion picture cameras wherein a rotary shutter can be arrested in two different angular positions in one of which it overlies and in another of which it exposes the aperture for admission of scene light to unexposed film frames.
German printed publication No. 2,002,699 discloses a motion picture camera wherein a rotary shutter can be arrested in two different angular positions. If the shutter is arrested in that angular position in which its blade overlies the light-admitting aperture, the duration of the exposure time corresponds to that interval which is required to rotate the shutter through a predetermined fraction of a single revolution. If, on the other hand, the shutter is arrested in that angular position in which the shutter blade is out of register with the light-admitting aperture, the film frame behind such aperture remains exposed to scene light for as long as the shutter stays idle, i.e., at the will of the operator who must depress a knob or otherwise manipulate a device serving to set the shutter in motion in order to allow the blade to again overlie the aperture and to thus terminate the exposure of that film frame which is in register with the aperture. Such exposures with "long" exposure times are often necessary for the taking of pictures in twilight or at night with artificial illumination of a subject or scene. The arresting or intercepting mechanism of the camera which is disclosed in the German printed publication employs a pivotable intercepting lever which cooperates with two cams on the shaft of the rotary shutter. The cams are angularly and axially offset relative to each other. When the lever is caused to engage one of the cams, the shutter is arrested in an angular position in which the blade overlies the light-admitting aperture. When it cooperates with the other cam, the lever arrests the shutter in that angular position in which the blade is out of register with the aperture. The lever is mounted on a sleeve which is reciprocable in parallelism with the axis of the shutter by means of a handle or knob which must be manipulated by the user of the camera.
French Pat. No. 985,406 discloses a motion picture camera wherein the arresting or intercepting mechanism for the rotary shutter comprises two discrete levers one of which must be actuated to arrest the shutter in a position in which the blade overlies the light-admitting aperture and at least the other of which must be actuated to arrest the shutter in that angular position in which the blade is out of register with the aperture. When the user wishes to make exposures with long exposure times, a knob must be depressed to effect simultaneous actuation of both levers.
German Utility Model No. 1,503,407 discloses an arresting or intercepting mechanism which employs a substantially L-shaped pivotable member mounted on a leaf spring and having several stop surfaces. One leg of the L-shaped member is biased by a spring against a knob which is depressible in the longitudinal direction of the one leg. Depending on the setting of the camera (for the making of exposures with relatively short or with relatively long exposure times), a depression of the knob results in larger or smaller displacement of the L-shaped member whereby the member first releases the shaft of the shutter and thereupon engages and arrests such shaft in the desired angular position.
A drawback of the just described conventional intercepting mechanisms is that they are rather bulky, complex and employ a substantial number of parts. Furthermore, the user of the camera must adjust the intercepting mechanism whenever he wishes to switch from the taking of pictures with long exposure times to the taking of pictures with short exposure times, or vice versa. Thus, the sleeve for the single intercepting lever of the camera which is disclosed in the aforementioned German printed publication must be shifted by hand so as to move the lever into register with the selected cam on the shaft of the shutter. In the cameras of the French patent and the German Utility Model, the knob must be shifted with reference to the intercepting member or members. Also, the cameras must be provided with detect means to prevent inadvertent changes in the position of the knob.